Update dependency @types/split2 to v4

Author: elastic-renovate-prod[bot]

package.json

@@ -59,7 +59,7 @@
     "@types/ms": "0.7.34",
     "@types/node": "18.19.64",
     "@types/sinonjs__fake-timers": "8.1.5",
-    "@types/split2": "3.2.1",
+    "@types/split2": "4.2.3",
     "@types/stoppable": "1.1.3",
     "@types/tap": "15.0.12",
     "chai": "4.5.0",